Mask holder



FIG. 1 is a front view of a mask holder showing my new design;

FIG. 2 is a rear view of the mask holder;

FIG. 3 is a right side view of the mask holder;

FIG. 4 is a left side view of the mask holder;

FIG. 5 is a top view of the mask holder;

FIG. 6 is a bottom view of the mask holder;

FIG. 7 is a bottom front side perspective view of the mask holder;

FIG. 8 is a top front side perspective view of the mask holder; and,

FIG. 9 is a side view of the mask holder in use.

The broken lines in FIG. 9 are illustrative of environmental structure forming no part of the claimed design. 

CLAIM The ornamental design for a mask holder, as shown and described. 